Transmission by direct skin or mucous membrane contact with
tissues and fluids of infected animals is less common.

Infection via inhalation of infective respiratory droplets
or aerosols is rare with naturally occurring plague in the United
States, but is the most likely route of transmission in a bioterrorist
event.

Becoming infected via inhalation requires direct and close
(within 6 feet) contact with an ill person or animal and has
not occurred in the United States for decades.